Oxidation of Cellulose Fibers Mediated by Nonpersistent Nitroxyl Radicals

Three different nonpersistent radicals bearing >NO center dot moiety have been used to oxidize the viscose fibers at room temperature and alkaline pH. The generation of the free radical species was achieved in situ, from their corresponding OH precursors: 1-hydroxybenzotriazole, violuric acid, and N-hydroxy-3,4,5,6-tetraphenylphthalimide. Three different routes were used: (i) in the presence of metallic cocatalyst (lead tetraacetate), (ii) under metal-free conditions (anthraquinone as organic cocatalyst), and (iii) a homolytically scission of -OH bond through a 365-nm UV irradiation. The oxidized fibers were subjected to attenuated total reflection FTIR characterization, potentiometric titration, wide angle X-ray, energy dispersive X-ray analyses, microscopic investigations, and solid-state C-13-NMR. The patterns of CP/MAS C-13-NMR spectra revealed that the oxidation occurred at the C6 primary hydroxyl groups of cellulose. Notably, as a result of the introduction of hydrophilic carboxylate groups, the water retention values of the oxidized fibers increased by 35% as compared to the original nonoxidized sample. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4790-4799, 2010